Electro-optic devices have in the recent past begun to employ electrode wafers as a part of the electro-optic system. Ceramic wafers having piezoelectric properties have been found to be suitable for devices in which the adjustment of voltage will adjust in some manner the transparency of the electroded wafer being used as a lens. For example, in the journal, Ferroelectrics, 1976, Vol. 10, pp. 47-51, a stereoscopic viewing system using PLZT ceramics in a new electro-optic shutter viewing device is described for use with stereoscopic real-time television and computer-driven CRT display systems. Other uses for ceramic wafers having piezoelectric properties include the use of these wafers as lenses in the goggles for protection against flash blindness.
One of the most important aspects in preparing an electroded wafer for use in electro-optic devices is to ensure that the electroded wafer responds in an optimum manner to the electronics of the system. This requires the application of an electrode to the wafer which is strong, durable, easy to apply, and effective.
It has been proposed in the past to apply surface electrodes such as in U.S. Pat. No. 3,609,002, in which a plurality of interconnected interdigital electrodes are placed on the surface of a ferroelectric ceramic material for use in an electro-optic system. As an alternative to the surface electrodes in the previously described reference, a three-dimensional effect is achieved in U.S. Pat. No. 3,540,427 where a technique for fabricating an array of very high-speed light deflecting units is described.
An improvement on this previously described patent is contained in U.S. Pat. No. 3,704,512, in which a plurality of parallel slots are cut into the body of an electro-optic crystal and filled with an electrically conductive foil that is made to adhere to the walls of the slot using an electrically conductive adhesive. Nevertheless, all of these prior art methods are inadequate to provide the plurality of electrodes in a ceramic wafer of sufficiently small size to permit use in the more sophisticated electro-optic systems presently envisioned. Applications of metal coatings themselves are well known in the art, as exemplified by U.S. Pat. No. 2,278,722, which concerns a method for obtaining, through a wet method and in the absence of an external electric source, a very adhesive deposit of a metal on a polished metal or on other surfaces such as glass, ceramic, metals, mica, or films of cellulose. U.S. Pat. No. 2,421,079, discloses a method for adhering metal to nonconductive materials such as glass, ceramics, leather, and other materials by the use of stannous fluroborate. Similarly, U.S. Pat. No. 2,757,104 discloses the use of stannous chloride as a sensitizing agent for depositing thin conductive films of metal to electrical resistors.
U.S. Pat. No. 3,011,920 discloses a method for electroless metal deposition used in the manufacture of printed electrical circuits and the like by the deposition on a clean substrate by catalyzing the substrate through a treatment with a bath containing collodial particles of a catalyst metal using palladium catalysts. Metal films of improved uniformity are disclosed in U.S. Pat. No. 3,798,050, using a buffered palladium solution in contact with the glass or other material being plated.
Nevertheless, it does not appear in the prior art a simple, efficient method for manufacturing an electroded wafer for use in electro-optic devices wherein the electrodes are strong, adherent, and sufficiently positioned with respect to each other to operate with the intender's electronic circuitry for which the electrode wafer would be useful.